This application describes the need for a new PET Camera for the PET Center at Columbia University College of Physicians and Surgeons. The Columbia PET Center is presently equipped with an ECAT47 scanner (CTI/Siemens), acquired in 1992. Several groups of investigators, from the Departments of Psychiatry, Neurology and Cardiology have initiated NIH-funded PET research programs with this instrument. The neuroscience PET program (psychiatry and neurology) is aimed at understanding the pathophysiology of severe neuropsychiatric conditions, including Alzheimer's disease, mood disorders, schizophrenia and drug abuse. The cardiology PET program is focused on coronary heart disease. Both programs use conventional flow and metabolism markers such as [18F]FDG and H215O. In addition, specific compounds radiolabeled with C-11 play an increasingly larger role in the program: (11C]acetate and [11C]palmitate for heart studies, and numerus neuroreceptor probes for brain studies, such as [11C]raclopride (dopamine D2 receptors), [11C]NNC 112 {dopamine D1 receptors), [11C]WAY 100635 (serotonin 5HT1A receptors), and [11C]McNeil 5652 (serotonin transporters). The performances of commercially available PET cameras have markedly improved over the last six years. The availability of a scanner with improved performance would be greatly beneficial to the various NIH- funded research projects described in this application, and will be crucial to maintain the scientific competitiveness of the Center. More specifically, the ECAT EXACT HR+ (CTI/siemens) represents a new generation of PET scanners, the first canner designed after full development of the 3D acquisition mode. The HR+ provides marked improvements in resolution (20-40%), sensitivity (20-30%), and count rate capability (60-70%), compared to our current instrument. Increased resolution in the 3D mode is critically needed to measure signal from small brain structures, such as the amygdala, hippocampus, and nucleus accumbens, that pay a crucial role in the pathophysiology of neuropsychiatric conditions under study. Increased sensitivity and count rate capability are critically needed for heart perfusion studies. A new generation scanner will provide improve resolution, axial sampling, sensitivity and count rate capability. These features will greatly improve the quality of the PET studies performed in our center. ultimately, these improvements will translate in better understanding and treatment of the medical conditions under study in our PET Center.